// 1px下划线的问题
@mixin border-1px ($color) {
    position: relative;
    &:after {
        display: block;
        position: absolute;
        left: 0;
        bottom: 0;
        width: 100%;
        border-top: 1px solid $color;
        content: "";
    }
};

@mixin bg-image ($url) {
    background-image: url('./imgs/'+$url+'@2x.png');
    @media (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio: 3) {
         background-image: url('./imgs/'+$url+'@3x.png');
    };
};